With every patient, we begin by looking into your ears with an Otoscope. We then follow up with our first type of hearing test - Pure Tone Audiometry. This measures the softest sounds that you can hear across the main frequencies that are important for hearing speech.
The test compares how well you hear these to normal hearing for a young adult population.
Pure tone audiometry includes both air and bone conduction testing. Bone conduction testing is only carried out if your air conduction thresholds are below normal.
It is vital that the hearing test is carried out in quiet conditions. Background noise will interfere with results. Here at Mills & McKinney Practice we only test hearing in sound-proofed rooms that conform with the latest standards.
Air conduction testing
Air Conduction testing is carried out using either headphones placed over the external ear, or insert earphones placed at the entrance to the ear canal.
Air conduction testing with headphones is shown below.
You will be presented with a number of tones – some louder, some extremely soft - and asked to press a button as soon as you hear the sound.
Your hearing threshold is where you just begin to hear sound, and the audiologist will check your thresholds very carefully until they are sure that they are accurate.
Air conduction audiometry measures the response of the entire hearing pathway – ear canal, middle ear, inner ear (cochlea) and more central auditory pathways.
The outer ear, ear canal, middle and inner ear are shown below.
Air conduction thresholds are measured before bone conduction thresholds. If a hearing loss is recorded with air conduction thresholds, it is important to know the cause. This is where bone conduction testing comes in.
Hearing loss could be due to a blockage in the ear canal or middle ear, or due to damage to the inner ear (cochlea).
The hearing loss is termed conductive if it is due to blockage in the ear canal or middle ear, and sensorineural if it is due to damage to the inner ear or central auditory nerves. Sometimes both conductive and sensorineural losses are present in the same person, in which case the hearing loss is termed mixed.
Common causes of conductive hearing loss are wax and middle ear fluid. Common causes of sensorineural hearing loss are age related hearing loss and noise induced hearing loss.
Bone conduction testing
Bone conduction testing helps to identify whether a hearing loss is conductive or sensorineural. Therefore whenever a hearing loss is measured by air conduction, bone conduction testing should be carried out.
During bone conduction testing a small bone-vibrator is placed on the mastoid bone behind the ear.
This sends sound directly to the inner ear (cochlea), shown below. In other words, the sound from the bone-vibrator bypasses both the ear canal and the middle ear.
If air and bone conduction thresholds are similar, then the hearing loss is sensorineural. If there is a significant difference between the thresholds, then the hearing loss is conductive.
Bone is an excellent transmitter of sound, and therefore even though the bone-vibrator is placed on one side of the head, the sound it transmits is sent to both cochleae simultaneously. The better hearing cochlea will usually respond. It is therefore not always possible to be certain which cochlea is responding without masking.
Masking is used when the audiologist is not sure which ear is responding to the test sound. Masking stops the non-test ear from responding to sound, so that the audiologist can be certain that the response is from the test ear.
A rushing sound is presented to mask the non-test ear at the same time as a test tone is presented to the test ear.
Air Conduction Masking
If the difference between air conduction thresholds between the two ears is 40 dB or more using headphones, then it is possible that the sound presented to the worst ear is reaching the better ear by bone conduction. The thresholds shown for the worst ear may therefore actually be a “shadow” of the thresholds in the better ear.
This is also a possibility when the difference between air conduction thresholds in the worse ear, and bone conduction thresholds in the better ear is 40 dB or more.
In both cases a masking noise is presented to the better ear to stop it from responding to test tones. This allows accurate measurement of the air conduction thresholds in the worse hearing ear.
Bone Conduction Masking
A masking noise is presented via a headphone or inset earphone to the opposite ear to the one tested by bone-conduction testing. This stops the non-test ear responding to sound. The audiologist can therefore be sure that the masked bone conduction threshold belongs to the ear where the bone vibrator is placed.
This measures the pressure of your middle ear, and how well the eardrum and middle ear bones move. It will show if there is any problem with the middle ear, including if there is middle ear fluid.
A small button is put into the ear canal, and you will feel a slight change in pressure. You may also hear a few tones and other sounds.
There are a number of different types of speech testing. These are very useful for predicting how well you are likely to do with hearing aids, as they measure how well you hear speech when the volume is corrected for your hearing loss.
Some speech tests measure how well you hear in noisy conditions, and these can be very useful for predicting whether you would benefit from wireless accessories, such as remote microphones or TV streamers. They can also indicate whether you have any difficulties with auditory processing.
Others measure how well you discriminate sounds as the volume increases. These are very good for identifying any problems with speech discrimination, including difficulties with auditory processing.
Otoacoustic Emissions (OAE)
OAEs measure the response of the cochlea to sound. This test is used for neonatal hearing screening, but also for adults.
Visual reinforcement audiometry (VRA)
VRA testing is suitable for babies once they have head control, for very young children, or for older children who struggle to respond to sound. The child sits on their parent/carer’s lap, and sound is presented from speakers on the left or the right. Every time the sound is presented, and the child looks towards it, they are rewarded visually with a lit up animated toy.
Once the child is a bit older, usually between 18 months and five years of age, they can be taught to carry out a simple fun task when they hear sound, for example put a cupcake into a tray, or a man into a boat. This is called play audiometry.
Results are recorded on an audiogram in the same way as for air and bone conduction testing.
Our specialist paediatric Audiologists here at the Portland are experts in getting reliable responses from even the most difficult to test children.
For further information on our Paediatric hearing care please see Children’s hearing assessment & management.
Specialist audiological tests
These include the following:
Auditory Brainstem Testing (ABR)
This measures the response of the auditory nerve. This test is often used for babies and young children who cannot respond reliably to sound.
Auditory Processing Test Battery
This consists of a number of tests which together measure auditory processing ability.
Cortical Response Audiometry (CERA)
This measures the response of the brain to sound.
Free field audiometry
Sound is presented through a speaker rather than by air or bone conduction. Results are recorded on an audiogram in the same way as for air and bone conduction testing.